The invention relates to vertical exhaust systems and exhaust water trap assemblies, including for heavy duty vehicles, such as trucks, tractors, off-road equipment, and the like which utilize a vertical exhaust system, for example in which the exhaust conduit extends vertically alongside the cab of the vehicle.
For reduced emissions, catalytic converters and soot filters have been incorporated in the exhaust system of buses, trucks, and so on. If the exhaust outlet is vertical there is a possibility that water, such as rain, snow, or bus or truck wash, can enter the upper end of the exhaust system and flow downwardly into contact with the catalytic converter or soot filter unit. The water entering the system can be absorbed in the catalyst/filter mounting mat, e.g. vermiculite, that is typically located between the outer surface of the catalytic converter and the outer body of the exhaust conduit. Mounting mat that is exposed to water results in a much lower push out force, a measure of the ability for the mat to retain the catalyst/filter in place. In another scenario, freezing of water in the catalytic converter can cause structural damage to the monolithic catalyst. As an additional problem, water flowing through the catalytic converter or soot filter may tend to wash particulate material downwardly where such material collects and clogs the lower surface of the catalytic converter/soot filter causing premature failure thereof.
One solution to the above identified problem is shown in U.S. Pat. No. 5,321,215, incorporated herein by reference. As shown in the '215 patent, a perforated tube 15 extends vertically axially within a housing having an outer tubular body 2, and exhaust flows upwardly through tube 15 then radially outwardly through a first Set of perforations 19 into an annular chamber 16 then vertically upwardly through such annular chamber and then radially inwardly through a second set of perforations 20 back into tube 15 and then vertically upwardly for discharge. The tube is closed by a plug or closure 21 between the upper and lower sets of perforations 20 and 19. An annular or ring-shaped deflector is mounted on the outer surface of tube 15 and is located immediately beneath plug 21 and intermediate the two groups of perforations 19 and 20. Any moisture flowing downwardly within the upper chamber 25 of tube 15 will flow outwardly through the lowermost perforations of the upper group 20 and be deflected radially outwardly by deflector 26 into the noted annular chamber 16 and be collected in a trap 27 above a lower flange 17, for drainage through a drain opening 28 in outer tubular body 2.
In another known solution to the above identified problem, a plurality of vertically upwardly extending inlet tubes circumferentially surround and axially overlap a downwardly extending central outlet tube, known as the Gatling Gun design. In this design, water entering the system through the outlet tube flows vertically downwardly therealong and does not enter the inlet tubes because the top ends of the inlet tubes are laterally offset from and vertically above the lower end of the central outlet tube.
The present invention provides another solution to the above identified problem. The present invention provides a short vertical axial length for easy vehicle packaging, freedom to modify outlet tube size and location, and further provides reduced backpressure and lower production costs. In one aspect of the invention, vertical height is shortened by eliminating internal exhaust tube portions. In another aspect, reduced backpressure is provided by eliminating the re-introduction of exhaust into a perforated exhaust tube prior to discharge, for example eliminating re-introduction of exhaust through the upper group of perforations 20 in the above noted '215 patent. In another aspect, backpressure is reduced by separating inlet and outlet exhaust tubes, and providing an open unobstructed plenum therebetween free of an exhaust tube otherwise extending axially therethrough. In another aspect, backpressure is reduced by separating the inlet and outlet exhaust tubes, to enable a larger inlet tube into a plenum providing a larger area for perforations, without limiting the diameter of the inlet tube to that of the outlet tube otherwise dictated by downstream system requirements. In another aspect, backpressure is reduced by eliminating 180° bends in exhaust flow otherwise required between axially overlapped laterally offset inlet and outlet tubes, such as in the above noted Gatling Gun design. In another aspect, the invention provides lower production cost by eliminating full circle leak-proof welds around each of a plurality of inlet tubes as in a Gatling Gun design, required to prevent water leakage therepast.